Tobacco curing system



Feb. 8, 1966 J. P. GRINNELL ETAL 3,233,883

TOBACCO CURING SYSTEM Filed Aug. 27, 1963 mw mm kw U 3; U Q K Mg U/NN INVENTORS John P. Grinnell Morrice E. Duil ATTORNEY United States Patent Ofi ice 3,233,883 Patented Feb. 8, 1966 3,233,883 TOBACCO CURING SYSTEM John P. Grinnell, Hastings on Hudson, N.Y., and Morrice E. Bail, Goldsboro, N.C., assignorsto Pyrofax Gas Corporation, New York, N.Y., a corporation of Delaware Filed Aug. 27, 1963, Ser. No. 304,839

5 Claims. (Cl. 263-19) 7 This invention relates to tobacco curing, and comprises a novel, portable tobacco curer assembly which is both simpler to operate and more efficient than any gas tobacco curer now in common use.

Eversince the 1860s, when tobacco growers first started to use artificial heating means for coloring and drying the tobacco leaf (these two steps being collectively termed tobacco curing), two general types of tobacco curing systems have evolved. The-first is the permanent installation used in conjunction with a tobacco curing barn, which involves a plant for producing hot gases, and ducts leading through the barn to exhaust vents over the roof of the barn, hot gases passing through the ducts heating the ducts and, hence, the air in the barn, affecting the necessary coloring and drying. The second general type of tobacco curing system involves one or a plurality of heaters disposed within the barn itself which are connected to a source of fuel and heat air directly as it passes through same, the hot air passing up and curing the tobacco hanging within the barn. These differ from bulk curing systems, which use the forced convection of air and are termed curing systems which create a natural flow of hot air. The present invention is of thelatter type.

In gas systems of this same general type currently available, 9 to -16'individual heaters are placedon the floor of .the barn and connected. to a common fuel source. Each heaterhas two burners: a small capacity burner is used to color the tobacco leaf and a high capacity, burner is used to dry the leaf. Different temperatures are necessary for each stage, in order to prevent the green color from setting, i.e., the leaf will only yellow while containing most of .its moisture.

Increasing theheat too slowly between stages causes running, redstreaks around the stems, and too fast an increasecauses scolding or sponging, the effect being brown streaks on the leaves. In practice, the operator may or may, not turn off each individual coloring burner, but in either case hemust turn on each drying burner as .he changes. the curing cycle from the coloring stage to the 2,170,735; 2,280,458 and 2,472,534. All of these prior art heaters have one or more burners centrally located near the bottom of the unit, combustion draws air upwards through the heater, and a deflection plate at the top distributes the heated air, prevents flames from igniting the tobacco. and keeps any falling leaves from getting inside the' burner, In each case, however, either no provision is made for the two different curing stages or the procedures for changing from one to the other are manual and cumbersome.

It is, accordingly, an object of the present invention to provide a tobacco curring system in which both stages of the curing operation coloring and dryingcan be performed with but a-single burner on each heater.

A furtherobject of the inv'entionis to provide a tobacco curer in which the fuel is more efficiently used, i.e., large volumes of air are heated to the required temperature without local overheating.

Another object of the invention is to provide a hot air ditfuser which distributes the hot air in a somewhat horizontal direction before it rises, thereby spreading the heated air more evenly throughout the curing barn.

A still further object of the invention is to provide a tobacco curing system which can go through both coloring and drying stages automatically or, alternatively,pcan be switched from the coloring stage to the drying stage by merely turning one valve for each system (i.e., for each barn).

Yet another object of the invention is to:provide.a tobacco curer the outside of which is sufficiently coolso as to be locatable adjacent the walls of a barn, and'in which the danger of accidental ignition of the hanging tobacco is effectively eliminated.

Various other objects and advantages will appear from the following description of an embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In essence, our tobacco curer "combines'Venturi and chimney effects to maximize the flow of air through a space heater for use in curingtobacco, and employsa high pressure burner designed to retain its flame within a small conical volume in front ofthe'nozzle (i.e., a simple gas orifice). The control system may employ a thermostatic control for maintaining pre-set temperatures'during each stage, and high and low pressure regulators for delivering fuel at the proper pressure for each stage; By using a burner with a maximum turndown ratio, it is possible to properly operate the single burner at both low and high pressures, thus effectingboth stages of thefcycle with a single burner, Alternatively, a single thermostat effective over the entire range (roughly, room temperature to 200 F.) can be used with fuel delivered at a single high pressure.

In operation, the flame from the burner is injected into a Venturi to inspirate outside air before the flame can dissipate its energy. The Venturi, or inspirating tube, is in an essentially horizontal plane (or at some angle-to the horizontal that is not vertical) and the products of combustion and the entrained inspirated air are discharged into an unobstructed vertical combustion chamber or chimney. This combustion chamber or chimney is open at the bottom and top and hot gases enteringthereinto from the Venturirise, creating a chimney effect, and thereby draw air in from the open bottom. The combustion chamber becomes hot and acts as a driving force for a second chimney coaxially surrounding the combustion chamber, and which is also open. Thus, air in the space between the vertical walls of the two chambers will be heated by the hot, inner combustion chamber wall and rises creating a second chimney effect. A diffuser is located over the top of the heater and, in the preferred embodiment, deflects the rising hot air in a generally horizontal direction.

It is believed that a better understanding of the invention will be gained by referring to the following detailed description of an embodiment thereof, takenin conjunotion with the attached drawings, and in which,

FIGURE 1 is a side sectional view of the curer, taken along line 11 of FIGURE 2;

FIGURE 2 is a front view of the embodiment shown in FIGURE 1; 1

FIGURE 3 is top view of the embodiment shown. in FIGURE 1; and

FIGURE 4 is a schematic diagramof a control system used to operate the invention.

With reference to FIGURES 1 through 3, it will be seen that the invention comprises a first chimney orcombustion chamber 1 which is a cylindrical piece of sheet metal open at both the top and the bottom. Chimney l is coaxially surrounded by chimney 2, which has the same general shape but is taller and wider than the first chimney. A Venturi indicated generally at 3 comprises two parts: a converging section 5 on the upstream end and a diverging section 4 on the downstream end. The Venturi 3 is mounted in the side of combustion chamber 1 at an orifice provided for same and it extends out through a suitable opening in the side of chimney 2. The Venturi is provided with a ring 6 or other suitable device for mounting the burner (not shown) in its open end.

A preferred diffuser, indicated generally at 7, cornprises a curved supporting segment 8 for holding the diffuser above the chimneys, and a semicircular, flat segment 9, and is fastened to one side of the chimney 2 and, if necessary, to supporting members 11. Segment 9 may also be slightly bowed, as shown in FIGURE 2. Other supporting members 10, 12 are provided, and the entire unit may be mounted upon a base 13.

It is to be understood that while the diffuser 7, as shown, has certain advantages in minimizing back-pressure and distributing the heated air directionally and horizontally, thereby achieving a more even distribution of air throughout the barn, other diffuser designs, such as a simple dished plate, could be employed. A separate function of the diffuser is to prevent falling leaves from entering the burner and igniting. Also, while the Venturi 3 is shown as entering the unit at a right angle, it could also be mounted at an angle declined from the horizontal without adversely effecting operation of the heater.

It is to be noted that the positioning of the burner at an angle to the chimney and confining the flame to a small volume with the Venturi has an added advantage, in that the danger of accidentally igniting tobacco with a poorly adjusted burner is elfectively eliminated. As noted hereinbelow, the double-chimney keeps the outer surfaces of the unit cool, adding to its safety.

The curer may be simply manufactured out of sheet metal of sufiicient gage thickness to Withstand the temperatures generated and normal usage and handling in a tobacco curing barn, by one skilled in the sheet metalforming art, by conventional procedures.

In operation, the burner is treated as a simple gas orifice. By injecting the flame (primary air being inspirated by the burner Venturi) into Venturi 3, secondary air and surplus air is inspirated into the open end of Venturi 5, the flame, combustion products and excess air traveling into chimney 1. The air and combustion products, being hot, rise through chimney 1, creating a chimney effect and drawing additional air through the open bottom thereof. After the unit has been in operation a short while the Walls of chimney 1 are heated, heating the air between chimneys 1 and 2; this creates a second chimney effect, and additional volumes of air are thus heated. By having the outer chimney 2 taller than the inner chimney 1, air from both have an opportunity to mix and reach a uniform temperature, although this is not a necessary feature of the invention. It is to be noted that, in operation, chimney 2 remains quite cool and as a result the heater may be placed adjacent to the walls of the barn without fear of fire hazard.

In the above-described embodiment of the invention, it was found that the proper heat for yellowing was achieved by limiting the delivery pressure to each burner to 11 inches water column; a satisfactory heat for leaf drying Was achieved allowing the pressure toincrease to 20 p.s.i.g. (the allowable maximum). Satisfactory heat input per unit varies from 5,000 to 6,000 B.t.u.s per hour for coloring, to about 35,000 B.t.u.s per hour for drying. It is also to be understood, of course, that the number of units used will vary with the size of the barn. Actual air temperatures generated will also vary with each individual installation, but approximately 90100 F. for yellowing to a maximum of 160l70 F. for drying is average.

The controls employed for operation of one embodiment of the invention are illustrated in FIGURE 4. A fuel supply 20, commonly liquid petroleum gas, is piped (in gaseous form, of course) to an ordinary 20 p.s.i. regulator 21, and then to .a safety valve 23 which is connected to a pilot generator 22 in series with a 190 F. high-temperature limit switch 24, the latter being located within the barn as a safety device only. A three-way valve 27 determines whether the gas flows through low-pressure regulator 25 or at 20 p.s.i. Thermostatic control 26 maintains the proper temperature at each stage by controlling the delivery pressure to the burners. In either event the gas flows from the valve 27 into burner 28 which is mounted in the orifice of the Venturi of the heater, indicated generally at 29. As will be obvious, any number of burners 28 may be connected to the valve 27 through suitable manifolding, and in this way'an entire curing barn (usually containing ten or more heaters) may be controlled by the single valve 27 when it is desired to switch the curing cycle from coloring to drying. In this manner, the operator need only light each burner once over the entire curing cycle.

An alternate control method employs only a single gas pressure and depends on thermostat 26 to maintain the proper temperatures. In this embodiment, the low-pressure regulator 25 and three-way valve 27 are eliminated. The gas travels at a single pressure (20 p.s.i.g.) to the thermostat 26. Thermostat 26 allows the gas to flow at full pressure to the burner (or burners) 28 until the barn reaches the pre-set temperature, and then lowers the gas pressure so that only suflicient gas to maintain that temperature is allowed to pass. From the foregoing it will be clear that the only practical function of low-pressure regulator 25 is to provide a positive control over burner delivery pressure during the coloring stage to insure that setting of the green color does not occur.

The proper number of burners are generaly permanently installed in the barn and connected to the external fuel source through suitable manifolds. In operation, the operator sets thermostat 26 for F. or so and lights the burners, which are run at either low or high pressure depending on which control system is being employed. In either case, when the pre-set temperature is reached the thermostat cuts the gas supply back to a level which maintains that temperature. When coloring is completed and drying commenced, the thermostat is reset for a slightly higher temperature (valve 27 being turned to high pressure if present) and, over a period of time, the temperature is incrementally increased to the aforesaid maximum of -170 F. A gradual rise in temperature is required during drying to prevent scolding or running.

To prevent local overheating within the barnand consequent setting of green in some of the leaves therein, it is advantageous to place the sensor for thermostat 26 at the first-tier level in the barn (i.e., at the level of the: lowest leaves).

In one unit of the type shown in FIGURES 1-3, operating with a 75 HP. Hones burner at 20 p.s.i.g., with a 7 /2 inch Venturi having a 3-inch throat, 4-inch exit diameter, and an outer chimney 16 inches long, a total air flow in excess of 18,000 cubic feet per hour has been measured. It is believed that this air flow through the unit was greater than for any gas tobacco curer of this type presently available.

It will be understood that various changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principal and scope of the invention as expressed in the appended claims.

Having thus described the subject matter of our invention What it is desired to secure by Letters Patent is:

1. A tobacco curer that comprises:

a first unobstructed chimney open at both ends and having an orifice near the bottom end;

a Venturi-type tube having one end connected to said first chimney at said orifice at approximately a right angle to said first chimney; a fuel burner disposed in the other end of said Venturi-type tube to provide combustion only within said tube and whereby only the products of combustion and inspirated air are discharged into said first chimney creating a first chimney effect to draw air in from said open bottom end;

a second chimney open at both ends and coaxially disposed around said first chimney and spaced therefrom, and having an orifice therein to allow passage of said Venturi therethrough, the top of said second chimney extending beyond the top of said first chimney to heat the air between said first and second chimneys creating a second chimney efiect and for mixing the air and said combustion products from said first chimney with the air from between said chimneys substantially within said second chimney;

a directional diffuser located above and secured to the top of said second chimney, said diffuser having a substantially flat, semicircular segment and a curved supporting segment attached to said second chimney; and

means connected to said burner for delivering 'fuel thereto.

2. The tobacco cure-r as claimed in claim 1, wherein said means for delivering fuel comprises;

a fuel supply;

a maximum pressure regulator connected to said fuel pp y;

a thermostat connected to said regulator; and

a distribution pipe connected between said thermostat and said burner.

4. An air heater that comprises:

a horizontally mounted burner unit that comprises a fuel delivery pipe disposed within an air-inspirating tube having a converging section nearest said pipe and a diverging section away from said pipe to provide combustion only within said tube;

a first vertical unobstructed chimney open at both ends and having an orifice in its side to which the end of said diverging section of said inspirating tube is attached whereby only the products of combustion and inspirated air are discharged into said first chimney creating a first chimney effect to draw air in from the open bottom end;

a second vertical chimney open at both ends coaxially disposed around and substantially taller than said firstoh-imney and spaced therefrom to heat the air between said first and second chimneys creating a second chimney effect and for mixing the air and said combustion products from said first chimney with the air from between said chimneys substantially Within said second chimney, said second chimney having an orifice in its side to allow passage of said inspirating tube therethrough; and

diffuser means located above said chimneys and secured to said second chimney for deflecting heated air rising therethrough.

5. The air heater as claimed in claim 4, wherein said diffuser means comprise,

References Cited by the Examiner 3. The tobacco enter as claimed in claim 1, wherein UNITED STATES PATENTS said means for delivering fuel comprises, 1,667,512 4/1928 Cruikshank fuel pp 1,848,150 3/1932 Becker 126-90 a maximum pressure regulator connected to said supply; 2 472, 534 6/ 1949 H 2 3 19 a thermostat connected to said regulator; 2,756,040 7/1956 Golden 26319 a three-way valve connected to said thermostat; 2,759,721 8/ 1956 Lee 263-19 a low pressure regulator connected to said three-way 2,840,362 6/1958 Krieble et al 263-19 valve and between said thermostat and said three- 2,8 1,38 7/ 19 Jones 26 19 way valve, whereby said three way valve controls 2,943,350 7/ 1960 Moseley the fuel pressure being fed to said burner; and a distribution pipe connected between said valve and said burner.

WILLIAM F. ODEA, Acting Primary Examiner,

CHARLES SUKALO, Examiner. 

4. AN AIR HEATER THAT COMPRISES: A HORIZONTALLY MOUNTED BURNER UNIT THAT COMPRISES A FUEL DELIVERY PIPE DISPOSED WITHIN AN AIR-INSPIRATING TUBE HAVING A CONVERGING SECTION NEAREST SAID PIPE AND A DIVERGING SECTION AWAY FROM SAID PIPE TO PROVIDE COMBUSTION ONLY WITHIN SAID TUBE; A FIRST VERTICAL UNOBSTRUCTED CHIMNEY OPEN AT BOTH ENDS AND HAVING AN ORIFICE IN ITS SIDE TO WHICH THE END OF SAID DIVERGING SECTION OF SAID INSPIRATING TUBE IS ATTACHED WHEREBY ONLY THE PRODUCTS OF COMBUSTION AND INSPIRATED AIR ARE DISCHARGED INTO SAID FIRST CHIMNEY CREATING AS FIRST CHIMNEY EFFECT TO DRAW AIR IN FROM THE OPEN BOTTOM END; A SECOND VERTICAL CHIMNEY OPEN AT BOTH ENDS COAXIALLY DISPOSED AROUND AND SUBSTANTIALLY TALLER THAN SAID FIRST CHIMNEY AND SPACED THEREFROM TO HEAT THE AIR BETWEEN SAID FIRST AND SECOND CHIMNEYS CREATING A SECOND CHIMNEY EFFECT AND FOR MIXING THE AIR AND SAID COMBUSTION PRODUCTS FROM SAID FIRST CHIMNEY WITH THE AIR FROM BETWEEN SAID CHIMNEYS SUBSTANTIALLY WITHIN SAID SECOND CHIMNEY, SAID SECOND CHIMNEY HAVING AN ORIFICE IN ITS SIDE TO ALLOW PASSAGE OF SAID INSPIRATING TUBE THERETHROUGH; AND DIFFUSER MEANS LOCATED ABOVE SAID CHIMNEYS AND SECURED TO SAID SECOND CHIMNEY FOR DEFLECTING HEATED AIR RISING THERETHROUGH. 